What phenomenon occurs when certain crystalline substances generate a minute potential difference under pressure?

• A. piezoelectric effect
• B. thermoelectric effect
• C. photovoltaic effect
• D. electrochemical effect

Answer: (A)

The phenomenon where certain crystalline substances produce a small potential difference when subjected to mechanical stress is known as the piezoelectric effect. This effect occurs in materials that have a non-centrosymmetric crystal structure, which allows them to generate an electrical charge in response to applied pressure or strain. This characteristic is valuable in various applications such as sensors, actuators, and microphones, where the conversion between mechanical and electrical energy is essential.

The other effects listed, while related to electrical phenomena, do not pertain to the generation of a potential difference through mechanical pressure. The thermoelectric effect relates to the generation of voltage due to a temperature difference, the photovoltaic effect involves converting light into electrical power, and the electrochemical effect concerns the generation of voltage through chemical reactions. Each of these has distinct characteristics and applications that separate them from the piezoelectric effect.